I believe my guarantor is Great Lakes and my loan

I believe my guarantor is Great Lakes and my loan (in default) is now handled by DCS. My question is this: I've read on several sites that I may request loan rehabilitation based on 9 payments of an amount that is "affordable and reasonable." When I speak to DCS they demand that I pay an amount far and above what I'm able to pay. I've established hardship for the purpose of lowering the amount that would be garnished from my paycheck and plan to make voluntary payments but can't I request a lower payment to rehabilitate my loan?